Side-by-side specifications of the Synology DS1621xs+ and DS1812+, from official datasheets. Differences are highlighted.
| DS1621xs+ | DS1812+ | |
| CPU | Intel Xeon D-1527 | Dual Core 2.13GHz |
| Cores / threads | 4 cores | 2 |
| RAM (base) | 8 GB | 1 GB |
| RAM (max) | 32 GB | 3 GB |
| Drive bays | 6 | 8 |
| Expandable to | 16 | 18 |
| M.2 slots | 2 | 0 |
| Network | 2x1GbE, 1x10GbE | 2x Gigabit |
| 10GbE | yes | no |
| Max raw capacity | 256 TB | 54 TB |
| Hot-swap | yes | yes |
| Form factor | desktop | desktop |
| Released | 2020 | 2012 |
Choose the DS1621xs+ if you want a much faster Intel Xeon CPU, far higher RAM ceiling, built-in 10GbE, and M.2 NVMe SSD cache support; it’s the clear performance/upgrade winner. Choose the DS1812+ only if you just need an older, basic 8-bay NAS with no 10GbE or M.2 and much lower headroom. The decisive tradeoff is modern speed and expansion on the 1621xs+ versus the older, simpler, cheaper 1812+.